Which evaluation criterion ensures proper positioning in the submentovertex projection?

In the submentovertex projection, the primary evaluation criterion for ensuring proper positioning is the symmetric appearance of the petrosae. This projection is designed to visualize the base of the skull, including the petrous ridges of the temporal bones. When the petrosae are symmetrical, it indicates that the patient's head is positioned correctly, which is essential for accurate imaging.

The petrous ridges should ideally be demonstrated in a symmetrical manner to confirm that the x-ray beam is perpendicular to the area of interest. If they are not symmetric, it may suggest that there has been some degree of tilt in the positioning, which could result in distortion or misrepresentation of anatomical structures important for diagnosis.

Other options like well-visualized maxillary sinuses or equal bilateral cochlea are important allusions for different projections or conditions but are not the primary indicators of correct positioning for the submentovertex view. The sella turcica should be in the midpoint for other projections like the lateral skull view, but in this context, it does not serve as the main criterion for positioning in the submentovertex projection.